Profiling of a log by use of cutter heads, and improved pulp chip produced thereby



Oct. 10, 1967' L. A. MITTEN 3,346,028

PROFILING OF A LOG BY USE OF CUTTER HEADS, AND Filed Aug. 8, 1966 IMPROVED PULP CHIP PRODUCED THEREBY LEONARD A. MITTEN INVENTOK gag,

ATTORNEYS 2 Sheets-Sheet 1 Oct. 10, 1967 L. A. MITTEN I 3,346,028

' PROFILING OF A LOG BY. USE OF CUTTER HEADS, AND

IMPROVED PULP CHIP PRODUCED THEREBY Filed Aug. 8, 1966 2 Sheets-Sheet 2 LEONARD A. MITTEN INVENTOR.

' ATTORNEYS United States Patent 3,346,028 PROFILING OF A LOG BY USE OF CUTTER HEADS, AND IMPROVED PULP CHIP PRO- DUCED THEREBY Leonard A. Mitten, Vancouver, British Columbia, Canada, assignor to Ernest E. Runnion, Shelton, Wash. Filed Aug. 8, 1966, Ser. No. 571,062 Claims. (Cl. 144-626) ABSTRACT OF THE DISCLOSURE A means and method employing a rotary cutter head for producing pulp chips from a conveyed log, and giving the pulp chips a rhombohedral shape with the top face, the bottom face, and the two side faces each lying parallel with the grain of the wood by the expedient of mounting the cutter head so that it rotates about an axis biased from the grain of the wood and takes a climb-cut slice from the log.

This invention relates to the profiling of logs by rotary cutter heads to obtain a cant suitable for the production of dimensional lumber, and to a new and improved pulp chip which is a by-product of the profiling. The log to be profiled is conveyed along a linear travel path, and the cutter heads occupy localized stations traversed by the conveyed log. The cant obtained from the profiling is one faced by four flats two of which parallel the logs vertical diameter and the other two of which parallel the logs horizontal diameter and thus locate each flat at right angles to adjacent flats.

In the cutting of chips from a log it is known that less power will be consumed by the cutter head if its cuts are made perpendicular to the grain than if the cuts parallel the grain. Moreover cuts which are made parallel to the grain cause a certain amount of brooming damage to the chips which is not present when cutting perpendicular to the grain. However, in a chipping operation which looks to the profiling of a log as its end object it is not possible to have the knives of the cutter head out at right angles to the logs axis for the reason that a concave face would then be generated upon the log. When a log is profiled by cutter heads for the above-described purpose of obtaining a cant which can be sawed to produce dimensional lumber, the faces generated by the rotating knives must be flat and this has been accomplished heretofore by mounting the heads so that the axis of rotation lies at right angles to the logs axis.

The present invention recognizes that in order to obtain the necessary fiat face the cutter head need not make its cuts parallel with the grain. A cutter head cocked so as to make its cut diagonal to the grain will also generate a flat face. Proceeding on this premise the problem has then become one of determining the angle of cock which, all aspects considered, is most satisfactory. I have conducted extensive tests to arrive at the answer, working with a cutter head mounted so as to be adjustably set in selected positions making a cut at various angularities, relative to the logs axis, ranging upwardly from the 0 which characterizes the cutter heads of existing profile mills. A lessened bruising of the produced chips is quite marked, and within certain limits this improvement is progressive as the angle between the cut and the logs axis increases. Chip damage is only barely visible at a cut angle of 37 and seemingly is completely absent at 45. It was found from graphs plotted during these tests that the power consumption curve drops significantly when the rotary axis of the head is angled 60 (a 30 cutting angle) from the axis of the log, and that from this point on, down to 45, the power reduction becomes propor- Patented Oct. 10, 1967 tionately greater. There is little difference as between the amount of power which is consumed to operate the cutter heads when the same are angled 45 and that which is required when the cut angle, relative to the l-ogs axis, is 7 increased beyond this figure.

Equally as important as the absence of bruising when considering the commercial value of the produced chip, I find that by an angling of the head the chip which issues from the profiling operation is given a rhombohedral shape and in consequence provides a greater exposure of end grain than does a rectangular chip. In this rhombohedral chip, i.e. a parallelepiped in which each of the six faces is a rhombiform figure, the grain of the wood runs parallel to the planes occupied by the two side faces and by the top and bottom faces. This reflects the planes along which shear divides the curved slices of the cutter heads first into cards and then into chips. The particular angle of the cutter heads cocking determines the degree to which the exposure of the rhombohedral chips end grain exceeds that of the conventional rectangular chip. This greater exposure has particular significance where the chips are to be used in a high-grade pulping operation.

With the above introductory in mind, it is the object of the present invention to provide a new means and method of profiling a log by the use of cutter heads, and as a by-product of said method producing a pulp chip superior to chips which cutter heads have heretofore produced.

The present application is a continuation-in-part of my application for Letters Patent of the United States filed June 1, 1966, Ser. No. 554,487.

Description of drawings In the accompanying drawings:

FIGURE 1 is a top plan view of one of a set of cutter heads mounted in accordance with teachings of the present invention to profile a conveyed log and as a by-prodnot of the profiling produce pulp chips of a rhombohedral shape. A showing of the log is incorporated in the figure.

FIGS. 2, 3 and 4 are fragmentary views schematically illustrating the card pattern of shearing along the grain produced by a cutter head knife as it bites into the log on one of a succession of cuts. The pattern here shown is for horizontal shear only. Included in FIG. 3 is a broken-line indication of a single one of the multiple chips into which each card divides. For the purpose of clarity the illustration in FIGS. 2 through 4 shows the slicing pattern which would be made by a single knife running the full length of the head whereas in a typical cutter head as shown in FIG. 1 the slicing cut is obtained by a plurality of knives located in a helical succession spaced at equidistant intervals of the heads circumference.

FIG. 5 is an enlarged view of a card to indicate the manner in which the same separates into chips. This view shows the vertical shear pattern which takes place. The terms horizontal and vertical as here used are relative and have meaning only where it is assumed that the slice is being taken either from the top or the bottom of a log.

Description of invention Referring to said drawings, the numeral 10 denotes a log in course of being conveyed within a profiling mill along a linear travel path through a station or stations occupied by cutter heads. Each of the cutter heads profiles a respective side of the log by removing a segmental portion of the log, the removed wood being in the form of pulp chips in that the cutter heads rotate in a climb-cut direction, namely in the direction of the logs travel, at a rotary speed so correlated to the log feed that the log advances the desired length of the chips in each revolution of the head. is-a highly desirable length for a pulp chip.

There are by preference four heads each producing a flat 12 upon the log, with two of the flats paralleling one diameter of the 10g and the other two flats paralleling a diameter lying at right angles thereto. Each cutter head is or may be of the type illustrated and described in my pending application filed Oct. 11, 1965, Ser. No. 494,633, wherein a plurality of disc sections 13 each carries a single chipping knife 14. The disc sections are keyed or otherwise fixed in side-by-side relation upon the live arbor 15 with the knives spaced apart circumferentially of the head.

The heads are or may be in pairs acting successively upon the conveyed log, with the two heads of each pair lying diametrically opposite one another. In the present invention it is the relationship which the rotary axes of these heads bear to the axial line of the conveyed log which is significant. As hereinbefore pointed out the rotary axes occupy positions cocked forwardly in the direction of the logs travel from a transverse vertical plane normal to the logs axis. The preferred magnitude of such cocking is 45.

In FIGS. 2 through 4 of the drawings I have shown the curved slice taken from the bottom or top side of a log by the related cutter head, and have indicated how this slice divides itself into cards 20 by what is termed horizontal shear. FIG. shows how each card breaks into chips 21 by what is commonly referred to as vertical shear. I repeat that horizontal and vertical as respects the plane in which the shear is effected presumes that the curved slice has been taken either from the top or the bottom of the log. I have transposed upon one of the cards in FIG. 3 a broken-line illustration of one such chip, and for correlating purposes have denoted by a and I) both on this chip and the chips of FIG. 5 the bevelled front face and the top face, respectively. These two faces, as with the bevelled back face, the bottom face, and the two side faces of each chip, each has very nearly the shape of a true rhomboid, which is to say a parallelogram with its angles oblique and the adjacent sides unequal. The grain of the wood parallels the planes in which the chips top, bottom, and side faces lie, such top and bottom faces perforce representing the horizontal shear lines along which the slices break into cards and such side edges perforce representing the vertical shear lines along which each card breaks into chips. It will be apparent that a rhornboidal shaped chip has the distinct advantage of exposing to the cooking liquor of a pulping operation a greater area of end grain than is obtained from a rectangular chip. With the 45 cut angle shown by x in FIG. 3 this exposure is approximately doubled.

I find it desirable to rotate the heads so as to give a knife speed no higher than 7000 f.p.m. Above this speed some bruising or brooming of the chips is evidenced. Using a 15" diameter head this knife speed is reached at 1800 r.p.m. With the log progressing through the cutter heads at A per revolution so as to obtain chips of this length, and assuming a head speed of said 1800 r.p.m. the log then has a speed of 112 f.p.m. The heads could of course be designed to take two outs per revolution and the feed speed could then be doubled.

Considering depth of cut, this is obviously limited by the geometry of the head in that the curved path of the knife must be such in relation to the log that the knife advances an amount at least equal to the advance of the log and the maximum depth must of course be less than the radius of the head. In actual practice the power that can be effectively transmitted to the head limits the cut to a depth something on the order of 3" to 4". Power consumption is directly proportional to the rate at which wood is consumed. In standard disc chopping, power consumption is a maximum (depending on species) of 600 hp. seconds per cu. ft. For rotary chipping, 400 hp. has been heretofore considered that the maximum. With the head angled to my preferred 45, I find that the power consumption is then a maximum of 300 hp. seconds per cu. ft. Douglas fir, one of the easier woods to chip, shows (with the angled head) a power consumption on the order of hp. seconds per cu. ft.

It is of moment to point out additional advantages which an angled cutter head obtains. Climb-out cutter heads mounted so that their rotary axes lie normal to the log axis tend to snake a log forwardly at a speed greater than the conveying speed. This overrun characteristic is especially difficult to control on short logs of very small diameter, particularly if the logs are wet. Angled heads materially reduce this overrun influence. There is also the advantage for flank-mounted heads, namely the heads which produce flats upon the sides of a conveyed log, that the downward thrust moment which they exert, when angled, reduces the force of over-head pressure which must be applied in order to hold the log seated in its guide-way.

It is my intention that no limitations be implied and that the hereto annexed claims be given the broadest interpretation to which the employed language fairly admits.

What is claimed is:

l. In a mill for profiling a log to remove a segmental portion thereof in the form of wood chips and leave a flat face upon the log: a support for the log, a rotary cutter head stationed so as to cut a curved slice of wood chips from a log occupying said support and having its axis of rotation angled from the axis of the log so as to lie diagonal thereto, and means for establishing between the cutter head and the supported log a bodily motion of the one relative to the other in which a succession of said slices are caused to be climb-cut from the log with a resulting progressive development of a flat upon the log.

2. Structure as claimed in claim 1 in which the cutter heads axis of rotation is angled approximately 45 to the l-ogs axis.

3. Structure as claimed in claim 1 in which the angularity of the cutter heads axis of rotation, relative to the logs axis, is no less than 45 and no greater than 60, approximately.

4. Structure as claimed in claim 1 in which said bodily motion is given to the log while the station occupied by the cutter head remains localized.

5. Structure as claimed in claim 1 having a second rotary cutter head formed and made to operate as a counterpart of the first-named cutter head and serving to produce upon the log a flat lying diametrically opposite and paralleling said flat which is produced by the firstnamed cutter head.

6. Structure as claimed in claim 5, the angularity of said cutter heads axes of rotation relative to the axis of the log being no less than 45 nor greater than 60, approximately.

7. In the profiling of a log, the method of employing a rotary cutter head to remove in the form of chips a segmental portion of the log and leave a flat face thereon, comprising conveying the log endwise to its length along a linear t-ravel path through a cutting station, and mounting the rotary cutter head at said station to have the head turn in a climb-cut direction about an axis biased from the axis of the log and in each revolution removing from the log as the latter traverses said station a curved slice of said segmental portion, which slice, by horizontal and vertical shear occurring along the grain of the wood, breaks up into multiple chips rhombohedral in shape, the flat face progressively developing upon the log as the product of a succession of said slicing revolutions.

8. The method of claim 7 in which the axis of the cutter head is biased from the axis of the log no more than 60 nor less than 45, approximately.

9. The method of employing a rotary cutter head to remove chips from a wood piece, comprising conveying the Wood piece generally endwise to its grain along a linear path through a cutting station, and mounting the rotary cutter head at said station to have the head cut into the wood piece in a climb-cut direction rotating about an axis biased from the grain of the wood piece and in each revolution removing from the conveyed wood piece at least one curved slice of wood, the slice by horizontal and vertical shear occurring along the grain breaking up into multiple chips rhombohedral in shape.

10. A method according to claim 9 in which the work piece bears upon a sustaining surface in its travel along said path and having the cutter head positioned so as to remove chips from a side face of the conveyed work piece exerting a thrust moment upon the work piece which is downward and forward.

References Cited UNITED STATES PATENTS Carlson 144--116 Clark 144-323 Clark 144172 Clark 144-326 Schubert 144172 Key 144-162 Schubert 144-172 XR Dickson 144326 Nilsson 144326 Altosaar 144-172 Traben 144323 15 WILLIAM w. DYER, 1a., Primary Examiner.

R. J. ZLOTNIK, Assistant Examiner. 

7. IN THE PROFILING OF A LOG, THE METHOD OF EMPLOYING A ROTARY CUTTER HEAD TO REMOVE IN THE FORM OF CHIPS A SEGMENTAL PORTION OF THE LOG AND LEAVE A FLAT FACE THEREON, COMPRISING CONVEYING THE LOG ENDWISE TO ITS LENGTH ALONG A LINEAR TRAVEL PATH THROUGH A CUTTING STATION, AND MOUNTING THE ROTARY CUTTER HEAD AT SAID STATION TO HAVE THE HEAD TURN IN A CLIMB-CUT DIRECTION ABOUT AN AXIS BIASED FROM THE AXIS OF THE LOG AND IN EACH REVOLUTION REMOVING FROM THE LOG AS THE LATTER TRANSVERSES SAID STATION A CURVED SLICE OF SAID SEGMENTAL PORTION, WHICH SLICE, BY HORIZONTAL AND VERTICAL SHEAR OCCURRING ALONG THE GRAIN OF THE WOOD, BREAKS UP INTO MULTIPLE CHIPS RHOMBOHEDRAL IN SHAPE, THE FLAT FACE PROGRESSIVELY DEVELOPING UPON THE LOG AS THE PRODUCT OF A SUCCESSION OF SAID SLICING REVOLUTIONS. 